Field of the Invention
The present invention elates to a perpendicular magnetic recording medium used in a hard disk drive (HDD) or the like, and a magnetic recording and reproducing apparatus.
Priority is claimed on Japanese Patent Application No. 2015-081658, filed on Apr. 13, 2015, the content of which is incorporated herein by reference.
Description of Related Art
A perpendicular magnetic recording method is, conventionally, a method suitable for improving the surface recording density, since it becomes more magnetostatically stable as the recording density becomes higher, which improves the thermal fluctuation tolerance. This is because by orienting the axis of easy magnetization of the magnetic recording layer, which was oriented in the in-plane direction of the medium, in the perpendicular direction of the medium, the diamagnetic field near the magnetic transition region, which is the border between recording bits, becomes smaller.
A perpendicular magnetic recording medium includes a soft magnetic backing layer (soft underlayer (SUL)), an underlayer, an intermediate layer, and a perpendicular magnetic recording layer sequentially laminated on a non-magnetic substrate. In the case in which the soft magnetic backing layer composed of a soft magnetic material is provided between the non-magnetic substrate and the perpendicular magnetic recording layer, the medium acts as a so-called perpendicular two-layered medium and thus can obtain a high recording capability. At this time, the soft magnetic backing layer plays the role of reversing the line of magnetic force generated from a magnetic head, and thus can improve the recording and reproducing efficiency.
In addition, since the underlayer is a dominant element that determines the particle sizes or orientations of the intermediate layer and the perpendicular magnetic recording layer provided thereon, selection of the material is extremely important in determining the recording and reproducing characteristics of a magnetic recording media. Therefore, various materials that are available for the underlayer are suggested. For example, it is possible to use an hcp-structured material or an fcc-structured material, such as a Ti alloy (for example, refer to Japanese Patent No. 2669529) or a NiFeCr alloy (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2003-123239), or an amorphous structured material, such as Ta. In addition, Japanese Unexamined Patent Application, First Publication No. 2010-92525 describes the use of an alloy including, as the underlayer, one of Ni, Cu, Pt, and Pd as the main component and as additive element, one or more of Ti, V, Ta, Cr, Mo, and W.
It is suggested that Ru be used as an intermediate layer (refer to Japanese Unexamined Patent Application, First Publication No. H07-244831). In addition, it is known that, since Ru has dome-shaped protrusions formed on the top portion of columnar crystals, Ru has an effect of growing the crystal grains of the recording layer or the like on the protrusions, promoting the isolated structure of the grown crystal grains, isolating the crystal grains, and thus growing magnetic particles in a columnar shape (refer to Japanese Unexamined Patent Application, First Publication No. 2007-272990).
In Japanese Unexamined Patent Application, First Publication No. 2012-069230, it is disclosed that a lamination structure of an fcc-structured alloy layer including an fcc-structured element and a bcc-structured element, and a NiW alloy layer is adopted for the underlayer.
In addition, in Japanese Unexamined Patent Application, First Publication No. 2004-227717, it is disclosed that TiV is used for the underlayer of a magnetic recording medium oriented in the in-plane direction.